add file streaming support

test_stream.py

@@ -0,0 +1,22 @@
+import stream
+import wave
+
+
+def test():
+    p = wave.record('-', stdout=wave.sp.PIPE)
+    f = stream.FileBuffer(p.stdout)
+
+    result = zip(range(10), f)
+    p.stop()
+
+    j = 0
+    for i, buf in result:
+        assert i == j
+        assert len(buf) == f.SAMPLES
+        j += 1
+
+    try:
+        for buf in f:
+            pass
+    except IOError as e:
+        assert str(e) == 'timeout'